1. Field of the Invention
The present invention relates generally to the design and use of medical devices, and more particularly to a method and system for establishing temporary access to a patient's vascular system for hemodialysis and other extracorporeal blood treatments.
Access to a patient's vascular system can be established by a variety of temporary and permanently implanted devices. Most simply, temporary access can be provided by the direct percutaneous introduction of a needle through the patient's skin and into a blood vessel. While such a direct approach is relatively simple and suitable for applications which are limited in time, such as intravenous feeding, intravenous drug delivery, and the like, they are not suitable for hemodialysis and other extracorporeal procedures that must be repeated periodically, often for the lifetime of the patient.
For hemodialysis and other extracorporeal treatment regimens, a variety of transcutaneous catheters and implantable ports have been proposed over the years. Transcutaneous catheters, such as the Tesio catheter available from Med Comp and the Perm-Cath.TM. available from Quinton, comprise a single catheter tube having a distal end placed in a vein in an in-dwelling manner and a proximal end which extends through the skin and is which available for connection to a hemodialysis or other blood treatment system. Such catheter includes a DACRON.RTM. cuff disposed just beneath the skin in order to reduce the risk of infection.
Implantable ports, in contrast, are entirely subcutaneous and connected to a vein or an artery by a subcutaneous cannula. Access to the port is achieved by percutaneous placement of a needle or other connecting tube. Such ports typically comprise a needle-penetrable septum to permit percutaneous penetration of the needle. Recently, several valved-port designs have been proposed, where introduction of a needle or other access tube opens the valve to provide flow to the cannula which connects to the blood vessel.
Both the transcutaneous and implanted port vascular access systems suffer from certain disadvantages and limitations. A particular problem with prior transcutaneous and implanted port vascular access systems has been replacement. It is often necessary to replace a transcutaneous catheter when its distal end becomes dysfunctional due to plugging or other causes. Heretofore, it has usually been necessary to remove the entire catheter, including the subcutaneous cuff which has become ingrown in the tissue. In the case of implanted port systems, either the port or the cannula attached to the blood vessel could become dysfunctional. Heretofore, it has generally been necessary to remove both the port and the implanted cannula when either needs to be replaced.
It would therefore be desirable to provide improved methods, systems, and kits which permit only a portion of an implanted system to be replaced when other portions of the system remain functional. Such improved methods, systems, and kits should both simplify such replacement procedures and reduce trauma to patient's undergoing such procedures. In addition, it would be desirable if the improved methods, systems, and kits were useful with a wide variety of implantable catheters (including at least subcutaneous catheters and transcutaneous catheters used for vascular access), were easy to use, and could reduce costs associated with long term maintenance of such implantable access devices. At least some of these objectives will be met by the different aspects of the present invention described below.
2. Description of the Background Art
U.S. Pat. Nos. 5,562,617 and 5,041,098 are exemplary of implantable systems employing cannulas extending between a port and a blood vessel for providing extracorporeal circulation. U.S. Pat. Nos. 5,417,656 and 5,281,199 show implantable ports which are connected to vascular cannulas via a transition region (FIG. 1A) and to a multiple branch cannula (FIG. 21). U.S. Pat. No. 4,892,518 shows an implanted port with a transition region extending to a cannula. U.S. Pat. Nos. 5,234,406 and 5,215,530 show two-piece catheters having a distal portion which can be placed percutaneously. The '406 patent discloses a large diameter proximal portion to enhance the flow rate of anesthetics to the subarachnoid region of the spine. U.S. Pat. Nos. 5,203,771 and 4,181,132 show implantable connectors which provide for percutaneous access to implanted shunts.
Related co-pending applications, assigned to the assignee of the present application, include Ser. Nos. 08/745,903; 08/724,948; 08/634,634; 08/539,105; and 60/036,124.
The full disclosures of each of the U.S. Patents and co-pending applications listed above are hereby incorporated herein by reference.